Process for the removal of mercaptans from petroleum naphtha



y 13, 1947- M. c. K. JONES 2,420,544

PROCESS FOR THE REMOVAL OF MERCAPTANS FROM PETROLEUM NAPHTHA Filed May 15, 1943 ADJUsi-MQNT 9 wnaeu.

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Bavarzbor 777mm C. K. Jorz5 Ex5 Clbuorngg Patented May 13, 1947 PROCESS FOR THE REMOVAL OF MERCAP- TANS FROM PETROLEUM NAPHTHA Minor 0. K. Jones, Mountainside, N. 3., assignor to Standard Oil Development Company, a corporation of Delaware Application May 15, 1943, Serial No. 487,139 2 Claims. (01. 196-32) This invention relates to the treatment of liquids with liquid treatingagents especially those immiscible or only slightly miscible with the liquid to be treated, and relates, more particularly, to an improved method for treating light mineral oils with a liquid treating agent.

stage than in conventional contacting methods.

In the treatment of heavy oils with immiscible treating agents, there have been many attempts to obtain thorough agitation. This is particularly advantageous when the agent has a deleterious local eifect unless carefully dispersed through the material being treated as, for example, in the treatment of oils with sulfuric acid.

However, in the treatment of light oils with liquid reagents, it has never been considered necessary to agitate the oil thoroughly with the reagent. In fact contact by blowing with air, stirring, shaking, or passing the reagent countercurrent to the oil has usually been considered sufficient. This is particularly true in the solvent extraction or caustic treatment of these light oils where one or two stages is conventional. Thorough agitation or mixing, such as is sometimes found necessary in acid-treating heavy oils, has not been considered desirable in the prior art.

It has now been found that the efliciency of light oil treating methods can be materially increased by effecting the intimate dispersion of one phase in the other by mechanical action wherein an unstable emulsion is formed which quickly breaks to insure adequate separation of the phases.

This method is not to be confused with the well known methods of adding the reagent to oils by drops or small streams, or forcing streams of the reagent beneath the surface of the oil. It should also be distinguished from methods by which the acid is sprayed by air or steam or other gases. By the term mechanical action is meant the mechanical dispersion of the oil with the treating agent under such conditions that the oil and the treating agent are subjected to a shearing action as a result of which the two phases break down into microscopically fine particles which are thoroughly mixed one with the other so that there more readily results the equivalent of a theoretical Physical or chemical action is accomplished more effectively than in conventional countercurrent packed towers so that such tall towers are not needed and much less space is required for equip ment.

This degree of subdivision may be produced by one of several different devices now available; for instance, it may be produced by means of a colloid mill, a homogenizing valve such as used in the food industry, or any other device-such as those in which a rotating disc operates against a stator with a very small clearance between the disc and the stator. or in which two stators operate in conjunction with an adjustable orifice. In any of these devices, the feeding pressure must necessarily be very high, probably of the order of 2000 to 5000 lbs. per square inch. The shearing stress of these devices greatly reduces the size of the globules leaving the device and enormously increases their number. It is of course understood that any other device which would give an equal intimate dispersion of the two phases is contemplated by this invention.

The homogenization or dispersion obtained by the present invention, in many cases, differs from that obtained in the food and other industries using such a, high degree of mechanical dispersion, particularly by providing for the preparation of a very unstable emulsion which promptly separates into the original phases, thus furnishing a very short time of contact between the treating agent and the oil. Two mutually insoluble liquids may be emulsified by mechanical agitation but will be unstable and will readily separate into the original phaseswhen (1) the emulsion contains more than 1% .of the dispersed phase and/or (2) the two liquidsare free from emulsifying agents. It is therefore eminently desirable that prior to mechanical agitation the liquids be freed of emulsifying agents and other impurities by careful distillation or filtration in the conventional manner.

Examples of other applications of homogenization in chemical engineering where subsequent immediate separation into the original phases is 3 not involved would be in the incorporation of addition agents such as anti-oxidants or inhibitors (some of which are diflicultly soluble), and in the production of emulsions in synthetic rubening of petroleum distillates with various reagents.

However, one of the most important applications of the present invention is in the field of her manufacture as in the contact o op 5 solvent extraction. For example the present inmethyl chloride and isobutylene. vention is particularly useful in the following sol- Liquid-liquid chemical and physical action by vent extraction processes: homogenization provides a method for controlling (a) Hydrocarbon extraction by sulfur dioxide the time and temperature of reactions in a man- (b) Hydrocarbon extraction by phenol ner which is not possible in conventional proce (c) Hydrocarbon extraction by furfural dures. There are numerous examples of liquid- ((1) Vapor phase absorption of isobutylene by liquid reactions utilized in petroleum technology sulfuric acid which can be carried out with greater efliciency (e) Extraction of butadiene and isoprene by than usual by the use of dispersion from mesuitable solvents. chanical action such as homogenization. (f) Extraction of mercaptans from gasoline For example, in the alkylation process for the with sodium hydroxide solution. production of aviation gasoline, isobutane is com- The single figure is a diagrammatic elevational bined with butylene to form saturated octanes view of the apparatus with parts in section. Rehaving high anti-knock qualities. This synthesis ferring 110W t0 this wi t r l to be is accomplished in the presence of a catalyst such treated such as naphtha introduced t ough line as strong sulfuric acid so that the reaction can I and a treating agent such as caustic soda inbe carried out at low temperatures with a minidu d t ou h e 2 a e mixed and p p mum of secondary reactions of t hydrocarbons into homogenizing valve 3. This valve consists of and sulfuric acid. It is customarily held that the block 4 having a bore 5 discharging into venturi alkylation reaction itself takes place either on the A conical s a 1 is provided at the lower end surface or Within the catalyst phase. Isobutane, 0f the bore and a valve em 8 o ab y a n ed although relatively insoluble in sulfuric acid, prein block 4 and is provided with an adjustment sumably should be present in the catalyst phase Wheel 9 and a head p d o p rate in bore to the maximum extent possible before the olefin 5 and t h valve se 1 to form a p t o comes in contact with the acid. Otherwise the Shearing Stresshe mixture of naphtha and olefins would themselves polymerize or react with caustic Soda introduced through Venturi 5 Passes the acid. However, when isobutane is present rethe Point of Shearing n e bo e 5 and is Withaction takes place between this isobutane and budrawn through line H and passed to a settler tylene formin t desired'octana By emulsifywhere the caustic is separated from the naphtha. ing the hydrocarbons and acid by means of a AS aneXample 0f t p oved results obtained homogenizer an extremely large acid urface i Invention when t0 the extraction exposed to the hydrocarbons present and any de- 0f mercaptans m a p t oleum naphtha, a com sired contact time is made possible simply by cir- Parison was made between t e esults obtained culating the emulsion. The alkylate produced 1n the usual batch agitation ethod and the becomes a part of and is recirculated with the 40 Process Fecording to s t on. Naphtha emulsion dissolved in the excess of hydrocarbons and Vanou? strengths of Sodium ydroxide were present, until removed by continuously withpumped slmultaneously through a valve-like drawing part of the emulsion, separating the acid mechamsm Set to eharge at 3000 lbs. P by settling, and distilling the hydrocarbons to r square inch. At the same time, portions of the obtain the various fractions. same naphtha were treated in a separatory fun- As another example of a liquid-liquid reaction nel us t n e V gorous agi at y which can be achieved more efiectively by the hand shaking. The results of these treatments present invention may be mentioned the sweetare set forth and compared in Table I.

TABLE I EXTRACTION or NIERCAPTANS FROM NAPHTHA wrTH' VARIOUS REAGENTS BY BATCH AGI'IATION AND BY HOMOGENIZATION Column Number 1 2 3 4 a 6 1 s 9 Treated with Sodium Hydroxide l1.2 Treated with I Potassium Hydroxide Untreated Be. 12.9 B6. Stock and Procedure Original Napkin Batch Batch 3000 #/Sq. In. Batch Batch 3000 #/Sq. In.

Treat 1 Treat 1 Homogenization Treat 1 Treat l Homogenization Operating Conditions:

Per cent Treat 10 20 9. 9 18.4 10 2O 9. 9 26. 4 Treating Temp, F 80 80 75 80 75 77 Gasoline Inspections:

Doctor Test Mercaptan sulfur, rug/ ml Per cent .Mercaptan Removed Reactive sulfur, mg./100 ml Peroxide Number Per c entRecovery Per cent Loss TABLE I--Continued Column Number Treated with Potassium Hydroxide, 6N .6 Be.

sium

, 29 H d Igobutyrate, 6N Potassium Stock arid Procedure y mm 6 Batch Batch 3000 #/St 1. In. Batch Batch 30 00 #/Sq. In. Treat 1 Treat Homogenl-zation Treat 1 Treat l Homogenization Operating Conditions:

Per cent Treat k. 0 10 9 18. 4 10 20 12. 9 25, 0 Treating Temp., F 80 80 80 80 80 so 32 e2 Gasoline Inspections:

Doctor Test Mercaptan sullur, mgJlOO m1. Per cent Mercaptan Removed active sulfur, mg./100 ml. Peroxide Number Gravity API Dist, N'agh.

I. B. F.:

l Three minutes vigorous agitation in the presence of nitro en g 1 Equivalent to sodium hydroxide solution (11.2 B6.) in OH" concentration.

8 DNP==does not pass.

From these data it can be seen that in all cases homogenization gave better mercaptan removal than did batch agitation. When these results are plotted on a curve 50 as to obtain exactly equivalent percentage treats, the improvement corre- 35.

data in columns 14, 15, 16, and 1'7 of Table I which 40 when extracting mercaptan from a naphtha conwere obtained when using a caustic solution containing a large amount of sulfur, presented in taining a solutizer. For a 10% treat, batch agi- Table II, the oil and the reagent being pumped tation did not give a product passing the doctor" through a homogenization valve as in the previous test, while essentially similar percentage treat by experiment.

TABLE II homogenization did give a sweet product, i. e., passing the doctor test. For a 20% treat batch agitation leaves a fractional content of mercap- .tans, while one stage homogenization gives a sweet product free of mercaptans. To secure a sweet product by batch agitation in further experiments required eight countercurrent stages.

Similar results are shown on the comparison between batch operation and homogenization Ex'rneo'rron or MERcAPrANs more Urrranernn HIGH 5mm Nemrm WITH Sonmrn Hrunomon SOLUTIONS BY Baron Aerre'rron' AND Bl? Horro- GENIZATION Column Number 1 2 3 4 5 6 7 8 9 Treated with Soglium Hydroxide, Treated'with Sgdium Hydroxide, Untreated 11.2 B. Be. Stock and Procedure Hi 11 Suliur Batch Batch 3000 #/sq. In. Batch Batch 3000 's In.

Treat I Treat 1 Homogenization Treat Treat l Homogenization Dperetion Conditions:

Per cent Treat Not treated 10 20 ll 23. 3 10 2o 11 19 Treating Temp... F 75 75 75 75 75 75 75 Gasoline Ins ections:

Doctor DNP DNP Mercaptan sulfur, mg./l00 ml 23 20 Per cent Mercaptan Removal 34 43 Reactive sulfur, mg./l00 ml Peroxide No Gravity, API.

Distillation N5 I. B. P.,

1 Three minutes agitation in the presence of nitrogen. DNP- doea not pass.

Treated with Solutizer Soln. 3N Potasi TABLE III Errncr or TIME or Aorm'rron' N PER CENT MER- CAPTAIN REMOVAL mom UNTREATED HIGH SULFUR NAPHTHA Usmc 10% BY VOL. or 11.2 Bit. NAOH Per cent mercaptan removal vs. time of agitation feed stock, 35 mg. mercaptan sulfur/100 ml.

Homogenization Time of agitation,Min.-.. 3 5 60 Per cent mercaptans removed 33 35 37 38 38.5 40 40 These data show that minutes agitation gives only a 7% greater mercaptan removal than 3 minutes of agitation. Although the 60-minute agitation did not give results exactly equivalent to a theoretical stage, it is evident that homogenization effected instantaneously the same percentage (40%) mercaptan removal as 60 minutes of batch agitation.

It is thus evident that this invention afiords an economical process for the contacting of two immiscible liquids assuring greater emciency with very short times of contact.

The nature and objects of the present invention having thus been set forth and specific examples of the same given, what is claimed as new and useful and desired to be secured by Letters Patent is:

1. An improved process for the removal of mercaptans from petroleum naphtha comprising mixing said naphtha with a solution of caustic, subjecting the mixture of caustic and naphtha to a mechanical shearing pressure between 2000 and 5000 lbs. per square inch obtained by forcing the mixture through the extremely small opening of a valve and immediately separating the caustic from the naphtha.

2. An improved process for the removal of mercaptans from petroleum naphthas by means of a solution of caustic comprising pumping said naphtha and said caustic through a common orifice at a pressure of 3000 lbs. per square inch and immediately separating the caustic from the naphtha.

V MINOR C. K. JONES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,311,593 Kalichevsky et a1. Feb, 16, 1943 2,080,737 Nutt et a1. May 18, 1937 2,323,616 McAfee et a1. July 6, 1943 2,325,052 Grosse et a1 July 27, 1943 2,164,665 Rogers et a1. July 4, 1939 1,621,475 Cross Mar. 15, 1927 Re. 17,719 Jones July 1, 1930 1,927,853 Stratford Sept. 26, 1933 1,816,528 Haysel July 28, 1931 2,169,545 Vose Aug, 15, 1939 2,381,293 LaLande Aug. 7, 1945 2,085,525 De Simo et a1 June 29, 1937 FOREIGN PATENTS Number Country Date Great Britain July 28, 1932 

